In a prior United States Patent Application, now U.S. Pat. No. 5,799,632, Easton Bennett taught how to improve heat transfer from a motor vehicle exhaust through the use of a tubular body having fluid impervious sidewalls formed out of a single length of conduit wound in a spiral coil. This structure brought the exhaust in closer contact with fluid to which a heat transfer was to be effected.
Experience has now shown that there are a variety of types of motor vehicles, the needs of which differ. In some makes of gasoline powered automobile the problem is one of heat management. A build up of heat occurs behind the catalytic converter and there exists a need to dissipate that heat. In contrast, diesel engines have a comparatively low heat production and there is a need to obtain maximum heat transfer from the exhaust gases that pass through the heat exchanger. In each case, there is a common problem of maximizing the rate of heat transfer, while avoiding heat build ups which could cause damage to the exhaust system or the engine.